Progressive migration of broken Kirschner wire into
the proximal tibia following tension-band wiring technique of a patellar
fracture: case report.

Abstract:

Wire breakage and migration is a known complication of using a wire
tension band construct to treat displaced patella fractures. We report a
case of a broken K-wire that migrated from the patella completely into
the proximal tibia without complication 9 years after the index surgery.
This report highlights the fact that wire migration can occur long after
fracture healing and be relatively asymptomatic. But because the
complications of wire migration can be deadly, it requires diligence on
the part of the physician to educate the patient that new knee pain
after operative fixation requires formal evaluation by the treating
surgeon.

Hardware failure and subsequent migration is a feared complication
of smooth wire fixation. A common application of cerclage wiring and
K-wires for a tension band construct is treatment of displaced patella
and olecranon fractures. Hardware irritation following these procedures
is common, while failure is less so. Rarely, this symptomatic retained
hardware can migrate causing potentially serious complications. We
describe a case of a broken K-wire that has migrated from the patella
into the proximal tibia and remained in position without complication.
The purpose of this case report is to bring attention to the treating
surgeon that migration of smooth wires may occur long after fracture
healing and can be relatively asymptomatic. Site of migration is
potentially problematic and may therefore require removal.

Case Report

A 48-year-old male underwent primary operative fixation of a
displaced, transverse patellar fracture of the right knee in May 1999
using a modified anterior tension band technique. Intraoperatively, two
1.6 mm K-wires and an 18 gauge cerclage wire were used for the tension
band construct. He was treated postoperatively in a hinged knee brace
locked in extension and allowed to weight-bear as tolerated. Early
active and passive range-of-motion in the hinged knee brace was started
at 2 weeks postoperatively after the surgical incision had completely
healed. The patient was completely weaned from the knee brace at 3
months postoperatively with no complaint of knee pain and had no
residual extensor lag.

Routine plain radiographs obtained approximately 1 year
postoperatively (August 2000) demonstrated K-wire and cerclage wire
breakage without displacement of the hardware (Fig. 1). The patient did
not complain of any knee pain and did not recall any incident of trauma
to the knee since the surgery. He was advised that serial radiographs of
the knee should be obtained to monitor for wire migration; however, the
patient was lost to follow-up for the next 7 years.

The patient returned to the office in February 2007 for evaluation
of mild, intermittent anterior right knee pain, and plain radiographs
demonstrated distal migration of the lateral K-wire (Fig. 2). Also noted
was a newly identified fatigue break through the proximal aspect of the
medial k-wire. Given the local migration of the hardware, the patient
was advised that all retained hardware should be removed secondary to
risk of migration into the intra-articular space potentially leading to
chondral damage as well as potentially migrating out of the knee joint.
The patient refused operative intervention at this time. He was then
advised that serial radiographs should be obtained to monitor for
further migration, but the patient did not return for follow-up until
2.5 years later (August 2009). The patient stated that his knee pain had
resolved. Plain radiographs at this visit demonstrated migration of the
lateral K-wire completely into the proximal tibia without migration of
the medial K-wire or the cerclage wire (Fig. 3). The patient has
continued to refuse removal of hardware despite having full knowledge of
the risks of retained broken K-wires and cerclage wires. The
investigators have obtained the patient's informed writ ten consent
for print and electronic publication of the case report.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

Discussion

Migration of broken K-wires after use in fracture fixation has been
reported in the literature for a variety of surgical procedures
including operative fixation of sternal fractures, acromioclavicular
joint dislocations, proximal humerus fractures, distal radius fractures,
finger fractures, and patellar fractures. (1-10) Complications arising
from migration of these K-wires have been as benign as migration into
adjacent soft tissue to as severe as migration into the heart causing
cardiac arrythmias, pericardial tamponade, and death. (4,11)

[FIGURE 3 OMITTED]

In a search of Medline, English language journals, three separate
case reports were identified that described four patients, each of whom
had undergone cerclage wiring of the patella (two patients had modified
anterior tension band (MATB) constructs, and two patients had
circumferential cerclage wiring) and subsequently experienced failed
hardware that migrated out of the soft-tissue envelope surrounding the
patella. (8-10)

Biddau and colleagues (8) described the migration of the superior
portion of a circumferential cerclage wire to the heart likely through
the venous system for which the patient had to undergo sternotomy and a
right atriotomy while on cardiopulmonary bypass. They recommended
consideration for removal of broken hardware in young, active patients
as they may incur higher risk of migration of fragments due to increased
motion about the knee joint. Furthermore, they recommended Doppler
ultrasound examination of any broken hardware that exhibited local
migration around the knee joint to evaluate the proximity of the wire
fragments to larger vessels. If proximity to a large vessel was noted,
they thought it might influence the surgeon's decision to remove
the hardware.

Choi and associates (10) described two cases of migration of broken
cerclage wire and K-wire. In both cases, the patients complained of pain
in the posterior aspect of the knee. In one case, they felt that
standard operative technique was not followed adequately because a
2-knot tensioning technique was used, and this may have resulting in
weakening the overall strength of the construct. This theory is not
supported in the literature as we were unable to identify any
biomechanical studies that suggested that 2 knots weaken the cerclage
construct. In their other case, they felt that too thin a K-wire was
used which weakened the construct although they state they were unable
to identify the exact size of the wire. Traditionally, if K-wires are
used to maintain the reduction, 1.6 mm K-wire are used. (1) In both
cases, they noted that the K-wires traveled through the subretinacular
tissue into the popliteal fossa in close proximity to the neurovascular
bundle.

Chen and coworkers (9) described a case of intra-articular
migration of a broken cerclage wire 3 years after the index surgery of
circumferential cerclage wiring of a comminuted patellar fracture in
which the patient presented with a swollen, painful knee. An arthrotomy
was performed to remove the intra-articular fragment. The investigators
felt that the cerclage wire was placed too posteriorly around the
patella; thus, when it broke, there was little to no posterior
soft-tissue buttress, and the broken wire easily penetrated through the
joint capsule. They recommended paying extra attention to place the
circumferential wire anterior in the substance of quadriceps and
patellar tendon so that adequate soft tissue remained between the wire
and the capsule.

In our case, a MATB technique was used with K-wires used to hold
the reduction. The K-wires were bent proximally around the cerclage wire
but were not bent distally. The patient initially complained of
intermittent anterior knee pain, and radiographs of the knee
demonstrated that the broken K-wire had migrated completely into the
proximal tibia. We believe the broken K-wire migrated during knee motion
and was driven into the proximal tibia. The wire remained
extra-articular and did not appear to damage the tibial chondral
surface. Migration into the proximal tibia may have been prevented had
we utilized the technique described by Wu and colleagues whereby both
the proximal and distal tips of the K-wire are bent around the cerclage
wire to prevent migration of the K-wire. (12)

Ultimately, it is important for the treating surgeon to be aware of
broken smooth wires about the knee after operative fixation of patellar
fractures given the complications that can arise from both local
migration and distant migration of the wire fragments. Local migration
of broken wire fragments into the intra-articular space may cause
irreversible chondral damage, and migration into the surrounding
soft-tissue and bone can be a source of knee pain. If wire fragments
migrate into the vicinity of the posterior neurovascular bundle, they
have the potential to lacerate the popliteal vessels and migrate
distally via either the venous or arterial system and act as emboli
causing damage to distal vessels or cardiac complications such as
cardiac arrythmia, pericardial tamponade, and death. (4,11) Knowledge of
these potential complications will allow surgeons to appropriately
counsel their patients for clinical and radiographic follow-up if new
knee pain arises after successful operative treatment of patellar
fractures and for serial radiographic follow-up if broken hardware is
noted even in the absence of knee pain.

Conclusion

When performing repair of patella fractures utilizing a K-wire
tension band technique, the patient should be counseled that hardware
breakage is a possibility and that a second operation may be necessary
to remove the broken implants. Other options include using alternative
fixation constructs such as screws or braided suture. These constructs
have been shown to be as biomechanically sound as their cerclage wire
counterparts and less likely to require removal. (13,14) We encourage
surgeons to counsel their patients that onset of knee pain after
successful treatment of patella fractures using smooth wires could
potentially signal wire breakage or migration and should warrant
clinical and radiographic evaluation. Once implant failure has been
recognized, serial radiographic evaluation of known broken wire
fragments should be undertaken to evaluate for wire migration even in
patients without knee pain. The combination of patient age, activity
level, and proximity of wire fragments to the intra-articular space and
the posterior neurovascular bundle should aid the surgeon in determining
if wire fragments should be removed.

Disclosure Statement

None of the authors have a financial or proprietary interest in the
subject matter or materials discussed, including, but not limited to,
employment, consultancies, stock ownership, honoraria, and paid expert
testimony.